There are many different types of electronic weighing scales (herein, “scales”) in use today. One popular type of electronic weighing scale is constructed with a platform for receiving the load to be weighed and a set of levers, pivots, flexures, or torque tubes to mechanically combine the forces applied to the platform by the load, thereby enabling the measurement of these forces with a single electronic load cell, which operates as a force transducer. The load cell is typically constructed with a mechanically-deformable sensor plate with one or more sensor elements bonded thereto. When a load is applied to the load cell, the sensor plate mechanically bends and the sensor elements bonded thereto produce an electrical output signal, the magnitude of which is commensurate with the load applied to the load cell.
Another popular type of electronic weighing scale is constructed with a platform for receiving the load to be weighed, and a plurality of electronic load cells disposed at the corners of the platform, or more or less evenly spaced along the periphery or marginal periphery of the platform, that supports the platform. Each of the load cells produces an electrical output signal indicative of the load sensed thereby. The electrical output signals of the load cells are averaged by processing circuitry associated with the scale to enable the load to be measured over a large area of the platform. The load cells can detect load using, e.g., variable resistance or variable capacitance. For example, U.S. Publication No. 2010/0307839 by Bradley describes capacitive load cells at the corners of the scale.
Combinations of the above schemes have also been disclosed. U.S. Pat. No. 4,458,770 to Bucci, for example, describes a linkage that mechanically transfers forces from the four corners of the scale to four centrally-located capacitive load cells. However, this scheme combines the disadvantages of each of the above schemes without providing new capabilities.
One problem associated with the multi-load cell scale described immediately above is that when the load is unevenly positioned on the platform, the load or force sensed by each of the load cells is not the same, with a disproportionate amount of the load or force being sensed by certain ones of the load cells. Consequently, the associated processing circuitry arrives at a weight calculation that is offset from the load's “true weight” determined when the load is centrally or optimally positioned on the scale.
U.S. Pat. No. 7,126,065 to Petrucelli describes locating the center of mass of an object on the scale by triangulation based on readings from the load cells at the corner. However, this scheme can only estimate the location of the center of mass of whatever has been placed on the scale. If multiple objects are placed on the scale, such as a triangle of three oranges in contact with each other and with the scale, their center of mass may be located outside any of them.